Improvements in the processing power of computers, storage systems, and the data intensive nature of enterprise applications have created a demand for access to high performance storage. While the external storage devices were initially based on the Small Computer System Interconnect (SCSI) standard, this technology, which uses a parallel interface, suffers from significant drawbacks in terms in speed and distance. Fibre Channel (FC) is a serial transport protocol developed for providing faster connectivity between computers and mass storage devices separated over larger distances. In FC, SCSI commands are encapsulated within FC frames and transported over FC links in FC SANs.
SAS is a relatively new serial protocol intended to replace parallel SCSI within an enterprise host or computer. SAS is specified in the American National Standard Institute standard referred to as Serial-attached SCSI, also known as ANSI/INCITS 376-2003, the contents of which are incorporated by reference herein. Both FC and SAS use 8b10b encoding and similar ordered sets. SAS employs a shared infrastructure with the ability to create a point-to-point connection between two devices through which data may be transferred without interruption. The SAS market is gaining increasing adoption, and SAS is becoming well-established in servers and internal storage. However, SAS is not expected to replace FC or Internet SCSI (iSCSI) as a network protocol due to the clear lack of maturity of SAS in the switching domain.
Classic Ethernet technology, on the other hand, has a very well-established and widely deployed switching infrastructure. This Ethernet infrastructure, however, suffers from a significant drawback in that it may lose frames due to congestion in network. Because of this unreliable nature of frame delivery, Ethernet technology was not natively used to transport storage I/O traffic. To overcome the unreliability, the iSCSI protocol was built using TCP/IP as a transport layer to carry storage I/O traffic over the unreliable Ethernet network.
Some of the drawbacks of classic Ethernet are addressed in advances by the IEEE. Enhanced Ethernet, being developed by the IEEE, provides per priority flow control and enhanced buffer management for congestion avoidance. The use of per priority flow control can enable separate classes of to be prioritized through the network depending on the importance of the data. In Enhanced Ethernet, the standard Ethernet frame is enhanced to carry this additional information, which will aid in overcoming the current drawbacks.
The emergence of Enhanced Ethernet provides a high bandwidth, low latency network that is highly suitable for carrying both regular Ethernet and storage traffic. Accordingly, there are techniques currently under development for carrying storage traffic over Enhanced Ethernet by encapsulating FC frames within Enhanced Ethernet (referred to as FC over Ethernet, or FCOE). FCOE is disclosed, for example, in U.S. Patent Application Publication No. 2006/0098681 filed on Mar. 10, 2005 and entitled “Fibre Channel Over Ethernet,” and U.S. patent application Ser. No. 11/514,665 filed on Sep. 1, 2006 and entitled “Fibre Channel Over Ethernet,” the contents of both which are incorporated by reference herein.
FIG. 1a illustrates exemplary conventional enterprise FC block storage network 100, with one or more physical servers 102, each with host bus adapter (HBA) 104 connected to one or more FC arrays 106 through FC switch 108. Any I/O requests from the server are sent through HBA 104 and FC switch 108 to disk drives in the FC array.
FIG. 1b illustrates exemplary proposed enterprise FCOE block storage network 101, with one or more physical servers 103, each with FCOE controller 112 connected to one or more FC arrays 106 through Enhanced Ethernet (EE) switch 114 and FC gateway 116. Because Enhanced Ethernet is loss-free and provides guaranteed delivery, Enhanced Ethernet is used to carry FC packets. Server 103, which generates a FC frame, uses FCOE controller 112 (or alternatively, an Enhanced Ethernet controller supporting FCOE traffic) to pass Enhanced Ethernet frames to EE switch 114. EE switch 114 passes the FCOE frames to FC gateway 116, which strips out the FC frames and delivers them to FC array 106.
FIG. 1c illustrates exemplary proposed enterprise FCOE block storage network 105 with one or more virtual servers 118 inside a single physical server 105 and connected to a single FCOE controller 112 connected to one or more FC arrays 106 through EE switch 114 and FC gateway 116.
In addition, multi-protocol controllers have been developed for communicating over SAS, Ethernet or FC, with Peripheral Component Interconnect Express (PCIe) as the host interface. For example, U.S. patent application Ser. No. 11/433,728 entitled “Intelligent Network Processor and Method of Using Intelligent Network Processor” filed on May 11, 2006, discloses a multi-protocol controller for communicating between either FC or Ethernet and PCIe. In another example, U.S. Patent Application Publication No. 2005/0013317, which claims priority to U.S. Provisional Application No. 60/487,007, filed on Jul. 14, 2003, discloses a multi-port Ethernet controller. However, because Enhanced Ethernet is so new, there are currently no controllers that combine both SAS and Enhanced Ethernet.